Saponification of materials consisting of or containing organic esters of cellulose



Patented Sept. 7, 1937' I SAPONIFICATION or MATERIALS'CONSIST- me or on CONTAINING ORGANIC ES- 'rn ts or CELLULOSE Robert Wighton Moncriefi', Frank Brentnall Hill, and Thomas Barnard Frearson, Spondon, near Derby, England, assignors to Celanese Corporation ofAmerica, acorporation of Delaware No Drawing. Application December 6, 1934, Se-

rial No. 756,285. In Great Britain December 9 Claims.

This invention relates to the treatment of cellulose acetate and other organic esters of cellulose and particularly to a process" for reducing the acidyl content of such esters. The invention.

is specially applicable to the saponiflcatlon of filaments, threads,- yarns, ribbons and the like made of or containing such esters. I It has been discovered that organic esters of cellulose can be saponified by means of nonmetallic bases, for example methylamine, ethylene diamine and other aliphatic amines, particularly those of low molecular weight, in the liquid phase with particular advantage, andthat by treating threads of cellulose acetate and like materials in this way specially desirable properties may be imparted to the materials. We have now found that the saponification of materials having a basis of cellulose acetate or. other organic esters of cellulose by means of non-metallic saponifying agents, and in particular methylamine and similar bases may be accelerated to a remarkable extent by the presence during saponiiication of copper. The copper is preferably added to the saponifying bath in the form of copper oxide or hydroxide, or a soluble cupric salt, for example copper sulphate. The copper may, however, be applied in other forms. Thus, a marked acceleration of the saponification has been obtained when the copper is initially present in the metallic state. .The organic ester of cellulose treated may be of normal or low viscosity, for example in thecase of cellulose acetate the viscosity maybe of the order of 30 to 50, 100, 200 or even higher,"

these figures being obtained by comparison of a 6% solution of the ester in acetone at 25 C.with glycerine at the same temperature taken as a standard of 100. Such esters of high viscosity may readily be made by methods in which degradation of the cellulose molecule is substantially avoided during acidylation, for example the.

methods of U. S. Patent No. 1,708,737. On the other hand, the viscosity of the cellulose acetate employed may be of the order of 10-20 or even lower, or between 20 and 30, measured on the scale referred to above.

The invention is of particular importance in connection with the saponification of" filaments, threads, ribbons, fabrics and like materials having a basis of cellulose acetate and will be described with special reference to the treatment of such materials.

The materials treated may be made by any suitable dry or wet spinning method. Where high tenacity is required in the final products it is of particular advantage to produce the filaments and the like by wet .spinning methods in the course of which they are stretched to a considerable extent, or to soften and stretch the materials after their production whether by' a wet or a dry spinning process. By applying the proc, ess of the invention to materials which have been stretched considerably, for example to 200% of their original length or even' more, materials of particularly valuable serin etric properties are obtainable.

Particularly good results are obtained by the .use of saponifying baths containing'methylamine and copper. Other strong aliphatic organic bases, for example ethylamine, propylamine,

amylamine and triethylamine, may also be employed. Again, somewhat weaker bases of the same series, for example trimethylamine. and allylamine, may be used. Further, considerably stronger bases of the same series may be employed, even very strong bases such as tetramethylammonium'hydroxide, provided care be taken to avoid damaging the materials. Again, amines containing more thanone amino group, and particularly aliphatic diaminesof relatively low molecular weight, for example ethylene diamine, symmetrical dimethyl ethylene diamine,. monomethyl ethylene diamine, and propylene diamine may also be used. Preferably at least one of the amino groups of such amines should be unsubstituted or mono-substituted. Amines containing more than two amino groups may also be employed, for example 1.2.3-triamino propane. The effect of one or more hydroxy groups in the amine appears to be to favour the penetration of the materials by the saponifying agent, and with this object in view substances of the type of owdiamino-p-hydroxy propane may be used with advantage. Again, bases of the heterocyclic series, for example piperidine may be used. Many of these bases appear to enter somewhat readily into combination with copper or copper salts. Some, for instance, readily dissolve copper oxide.

The remarkable accelerating effect of copper may advantage to effect saponification 20 C. and 25 or 30 C.', but when a high degree of saponification is to be effectedit is preferable to work at a somewhat higher temperature, e. g. -60" C. or 70C. or even higher depending on the boiling point of the solution. With a view to preventing excessive-evaporation of the base it is of advantage, particularly lwhen working at relatively high temperatures, to cover the surface of the saponifying bath with a layer of an oil, wax or like substance which is immiscible with the bath. The concentrations and temperatures employed in particular cases will naturally depend upon the properties of the particular base employed. In general, the conditions may be chosen so that the desired degree of saponiflcation may be effected by means of a treatment lasting from 1-2 minutes or less up to 3 or 4 minutes. On the other hand the treatment may be more protracted.

When the saponifying agent is applied to the materials in the form of an aqueous solution, it is convenient to incorporate the copper, for example in the form of cupric oxide or of a-watersoluble salt, for instance copper sulphate, in the saponifying medium itself. It is not, however, essential that the copper should be introduced in this way. It may, for instance, be applied to the materials prior to the application of the saponifying agent, or even introduced into the spinning solution from which they are made.

A very considerable acceleration of the saponifying process may be effected by the presence in the saponifying bath of quite small concentrations of copper, e. g. '0.01-0.05% 'on the weight of the bath or even less. 0n the other hand somewhat higher concentrations may be employed, e. g. 0.1% or 0.5%. These figures are based on'copper present in the cupric form. Since it is undesirable that the final product should contain substantial quantities of copper it is preferable to work with the smallest quantities capable of giving the desired result.

The saponifying medium may also contain swelling agents, solvents or latent solvents for the cellulose .ester, for example cyclohexanol, methyl cyclohexanol, glycerol, ethylene glycol and its mono methyl and dimethyl ethers, di-

acetone alcohol, benzyl alcohol, acetone, dloxane or methylene ethylene ether.

When the materials are treated in the form of filaments, threads, yarns and the like, it is of in warp formation", 1. e. by drawing a large number of ends through the bath in substantially parallel relationship one to another and in the same plane. Thus, yarn may be drawn from a creel by means of rollers or like devices extending across the entire assembly of ends or so-called warp and immersed or partially immersed in a bath containing the saponifying agent, through a reed into the bath, and after passing through the bath the materials may be drawn by a second roller, pair of rolls'or the like, situated outside the bath, through a. reed and out of the bath, whence they are forwarded to suitable collecting means or to means for effecting any subsequent treatment to be applied. Preferably the materials are washed and dried before being wound.

The saponifying agent may be applied by other means. Thus, for example, the materials in hank form may be suspended from rods which are caused to traverse the length of the bath, and at the same time to rotate so as to expose each portion of the yarn to the same depth in the bath for the same period. Again, the mate- -penetration of. the saponification agent.

may comprise the application of water to the 35 rials may be treated in the form of bobbins, cheeses or other packages. Any suitable means may in fact be adopted in applying the saponifying agent to the materials. Materials in yarn or like form may be treated continuously with their production and/or with a stretching step. Again, in the case of such materials, stretching may be effected during saponification or, provided saponification has not been carried too far, after saponification. In general it is necessary to soften the materials to enable them to be stretched to the desired extent, and in choosing a suitable softening agent due regard should be had to the extent to which the materials have been saponified.

As indicated above, the materials may be saponified in fabric form. This may conveniently be effected by passing the fabric continuously through a bath containing the saponifying agent, for example in an apparatus of the type of the winch dyeing machine.

It is generally advisable to treat the materials after saponification so as to remove any copper remaining therein. Any suitable means may be adopted for this purpose. A convenient 2 means comprises washing the materials with dilute sulphuric acid. Dilute aqueous solutions of other acids may also be employed for this purpose, for example a. solution of acetic acid of a concentration fectivef The materials prior to saponification may be subjected to a treatment adapted to facilitate This materials, or they may be treated with aqueous wetting agents, for example soaps.

The degree of saponification effected may be sufficient to reduce the acidyl content of the ester by 8-10% or even less. but is preferably some- 41 what higher, for example sufficient to reduce the acidyl content by 20-25% or 30%. Considerably higher degrees of saponification may be effected sufiicient to remove 35 or 40 to 50 or 55% of the acidyl content or more, even up to complete saponification, according to the particular purpose in view. Generally speaking, a loss in acidyl content of 20-25 or 30% is capable of rendering the cellulose acetate material insoluble in acetone and imparting to it a high aflinity for cotton 5 dyes without destroying the ailinity for cellulose esterdyes, for example the so-called S. R. A. dyes. The material may be rendered insoluble in substantially anhydrous acetone but may be soluble in acetone containing a considerable percentage, 5

e. g. 25-30%, of water. Or saponification may render the material insoluble in such mixtures as well as in anhydrous acetone. The saponification may raise the safe ironing point considerably.

Materials saponified according to the invention 6 may have, in addition to the valuable properties referred to above, a high tenacity and elasticity and a good extensibility. Such materials are of particular value for use in the manufacture of high twist yarns. tially saponified according to the invention have been found particularly useful as weft in the manufacture of crepe fabrics. Again, by the process of the invention, it is possible to obtain completely saponified materials of excellent tensile properties.

The following examples illustrate the invention:-

Example 1 Cellulose acetate yarn is led continuously in about 20% has been found ef- 3( Thus, high twist yarns parwarp formation from a creel through a saponifyin bath containing a 15-25% aqueous solution of mono-methylamine to which has been-added a sumcient quantity of copper hydroxide to produce a concentration 011105 to 0.5% copper. The

temperature of the bath is maintained at 25-30 C. and the rate of travel is adjusted so that the yarn is in contact with 'the bath for 2-3 minutes. In this way a yarn of good tenacity and extensibility having a relatively high safe ironing point and a good afllnity for cotton dyes may 'be obtained with relatively little loss of weight.

Example 2 The process is carried out as described in Example 1 exceptthat the saponifying bath is maintained at a temperature of 50-60" C. In this way the yarn may be saponified to a considerably greater extent than that treated according to Example 1.

Similarly other non-metallic bases, for example ethylamine, propylamine, ethylene diamine or others of the bases referred to above may be applied. I

2 Although the invention has been described with particular reference-to the treatment of materials having a basis of cellulose acetate, it is also applicable to the treatment of other materials containing other saponiflable esters of cellulose,

30 for example cellulose formate, propionate, butyrate, ethyl cellulose acetate, oxy-ethyl cellulose acetate and nitrocellulose acetate.

? What we claim and desire -to secure by Letters Patent is:-.-

a -1. Process for reducing theacidyl content of an organic ester of cellulose, which comprises treating the ester, in the presence-of copper in solution, with a saponifying agent therefor which is a non-aromatic nitrogenous organic base which contains less than '1 c'arbon atoms.

2. Process for reducing the acidyl content of an organic ester of cellulose, which comprises treating the ester, 'in the presence of copper in solution, with. a saponifying agent therefor which is a water-soluble nitrogenous base having less than 7 carbon atomsin which each carbon atom that it directly attached to a. nitrogen atom is directly attached to three other ,atoms apart from said nitrogen atom. g

3. Process for saponifyingfilaments, threads.

ribbons and like materials having a basis of organic ester of cellulose, which comprises treating thematerials in th presence oi. copper in solution with an aqueous solution of a saponifying agent therefor which is a non aromatic nitrogenous organic ba'se'which contains less than 7 carbon atoms.

4. Process for saponifying filaments, threads,

' ribbons and like materials having a basis of an organic ester of cellulose, which comprises treating the materials", in the presence of copper in solution, with an aqueous solution of a saponifying agent therefor which is a water-solublenitrogenous base having less than '1' carbon. atoms in which each carbon atom that isdirectiyattached to a nitrogen atom is directly attached to three other atoms apart from said nitrogen atom.

5. Process for saponifying filaments, threads.

ribbons and like materials having a basis of cellulose acetate, which comprises treating the materials in the presence of copperin solution with an aqueous solution oil a saponifying agent therefor which is a non-aromatic nitrogenous organic base which contains less than 7 carbon atoms.

6. Process for saponifying filaments, threads, ribbons and like materials having a basis of cel-. lulose acetate, which comprises treating the materials, in the presence of copper in solution, with an aqueous solution of a saponifying agent therefor which is a water-soluble nitrogenous base having less than '1 carbon atoms inwhich each carbon atom that 'isdirectly attached to a nitrogen atom is directly attached to three other atoms apart from said nitrogen atom.

7. Process for saponifying filaments, threads, ribbons and like materials having a basis of cellulose acetate, which comprises treating the materials with an aqueous solution of mono-methylamine in the presence of copper in solution.

8. Process for sap'onifying filaments, threads,

ribbons and like materials having a basis of cellulose acetate, which comprises treating the materials with an aqueous solution of mono-ethylamine in the presence of copper in solution. 9. Process for saponifying filaments, threads,

ribbons andlike materials having a basis of.celluiose acetate, which comprises treating the materials with an aqueous solution of mono-methylamine containing .0.05-0.5% of copper in solution.

ROBERT WIGHTON MONCRIEFF.

FRANK BRENTNALL HILL.

THOMAS BARNARD FREARSON. 

